1. Field of the Invention
The present invention relates to a voltage regulator, and more specifically, to a test circuit of a voltage regulator.
2. Description of the Related Art
FIG. 2 illustrates a block diagram of a related-art voltage regulator.
The related-art voltage regulator includes a reference voltage circuit 2, a voltage divider circuit 3, an output transistor 4, a differential amplifier circuit 10, and a constant current circuit 11, and is configured to output a predetermined output voltage Vout based on an input voltage Vin.
The voltage regulator includes a protection circuit 13 used for overcurrent protection or overheat protection. The protection circuit 13 is an important circuit for protecting the circuit of the voltage regulator, and is therefore required to be high in accuracy. Thus, in a manufacturing process, characteristics of the protection circuit 13 are measured to adjust the accuracy. The voltage regulator includes a test circuit or a test terminal used for this adjustment.
Further, the voltage regulator is required to be low in current consumption, and hence, for example, it is necessary to accurately adjust a tail current 110 of the differential amplifier circuit 10. In general, the tail current 110 is adjusted through trimming of a transistor included in the constant current circuit 11 (see, for example, Japanese Patent Application Laid-open No. Hei 04-195613).
However, the tail current 110 is a constant current to be used only inside an integrated circuit, and hence there is a problem in that a terminal for measurement is necessary for accurately adjusting the tail current 110 and the area increases accordingly.